Disclaimer: This is intended only to provide only the most basic understanding of what SCORM is.
SCORM (Shareable Content Object Reference Model) is a world-wide standard set of specifications for communication between elearning content and learning management systems.
A learning module using SCORM version 1.2 can communicate the following:
Additionally, a manifest packaged with the module tells the LMS (Learning Management System)
Examples of messages conveyed by SCORM communication:
The API Adapter translates and relays commands to the LMS.

An API adapter is simply a Java or flash object sitting somewhere in the browser window, often in a hidden frame. You can think of it as a translator between Javascript and whatever language the LMS understands.
Learning Module and Manifest = minimum package
To create the simplest SCORM-compliant module, commands are added to key events in the module, such as when the page opens and closes, which tell the LMS to open or close a communication session, and to set the status of the lesson correctly.
The LMS must have some way of knowing the structure of the course, and where to find the different pieces, so a "manifest" must be created for EVERY SCORM course. This is simply an xml file which details the course structure and which resources are associated with each piece of the structure.